In the prior art there are known a great many chemical compounds having antitumor activity, derivatives of 5-fluoruracil being among them, for example, 1-carbamoyl-5-fluoruracil (Japanese laid-open Application No. 148365/75), 1,3-bis(2-tetrahydropyranyl)-5-fluoruracil (Japanese laid-open Application No. 77072/77), 1-(2-tetrahydrofuryl)-3-cyanoethyl-5-fluoruracil (Japanese laid-open Application No. 77070/77), and 3-acyl-5-fluoruracils (Japanese laid-open Application No. 91880/77).
The most active among the known cytostatics, the derivatives of 5-fluoruracil, are fluorafur-1-(2-tetrahydrofuryl)-5-fluoruracil (U.S. Pat. No. 3,635,946), FUDR, 5-fluoro-2'-desoxyuridine (U.S. Pat. No. 2,949,415) and also FUDA, 5-fluoro-2'-desoxyuridine-5-carboxylic acid (J.Med. Chem. 12, 173, 1969).
A disadvantage of fluorofur is its certain neurotoxicity which, according to reports in the literature, is due to the products of decomposition of the preparation during its metabolism in the living body (S. K. Germane, A. A. Kimenis, Experimental and Clinical Pharmacotherapy, Riga, 1970, issue 1, p. 85-92). As far as FUDR is concerned, its synthesis is complicated and hence expensive, which hinders its wide use in practical medicine. The same applies to FUDA as well, whose synthesis is based on FUDR.